Project GTDI: Efficiency Increase

August 29th, 2011

Text and Photos by Diesel World Staff

Snow Performance was very thorough in making sure the Stage 3 MPG Max Boost Cooler arrived with everything to perform the install (minus the tools).

Our 1.9L Gets a Snow Water-Methanol Injection and Gains 5 Mpg

For the time being, no more cheap paint or free car washes for Project GTDI. We are now turning our attention to where the Volkswagen diesel needs the most help—our sub-100 hp 1.9L TDI under the hood.

Although a lot of people would love having a commuter that averages about 43 mpg, we want more. For safety purposes, a few extra ponies to keep from clogging traffic when we need to merge onto the highway would sure be a help.

We had a hunch the factory muffler was one of the exhaust's major restrictions, so we took Project GTDI to CGS Motorsports, in Chino, California, where it was removed.

The parts may be smaller, but the VW is still a diesel and operates on the same principles. Starting with the basics as you would with a Cummins or Duramax, the first thing we wanted to do was free up some air. The intake side was addressed in the last Diesel World issue with a drop-in K&N filter, along with removing some of the airflow obstructions on the factory airbox. Because we hadn’t touched the exhaust side yet, that was next on the list.

We called out a favor to CGS Motorsports, based out of Chino, California, and had their crew put our 2001 Golf up on the lift to take a better look at the underside. Exhaust tubing was mandrel-bent from the factory and was large enough to support the small diesel, so we had CGS straightpipe the VW and then dump it in front of the rear tire. CGS said if there were enough interest, they’d look into producing the GTDI’s system.

An inspection revealed mandrel-bent tubing from the factory and a rusted muffler clamp that CGS repaired before taking measurements.

Sans-muffler, the Golf picked up 1.4 mpg, although it accomplished this with a lot noise ,since the resonating tip is found on the driver’s side.

That inconvenience aside, we also saw a 30-degree drop in EGTs, according to the VAG-COM logs. While we didn’t get baseline dyno numbers, midrange spool-up was noticeably quicker; the top end also benefited greatly, giving us our first glimpse of potential (we were almost pressed back into the seat under full throttle).

This taste of performance still on our metaphorical lips, we justified a Stage 3 MPG Max Boost Cooler water-methanol injection from Snow Performance to pick up power, as well as economy, and then took it to The Diesel Shop, in Mission Viejo, California, for the install.

As we’ve come to expect from Snow Performance, the Stage 3 MPG MPX box came packed with every last piece of hardware necessary and a 2.5-gallon tank. The Diesel Shop had us back on the road within a few hours, at which time we began playing with the unit.

The baseline tuning suggestion for the MPG Max’s 2D mapping had the smaller sprayer on the two-nozzle system help increase the fuel economy about 3.5 mpg. Already happy, but still seeking more, we tweaked the mapping to generate an overall gain of 5.6 mpg when we dialed it in.

All the talk of tuning and switching programs may seem intimidating to some, but Snow Performance has simplified the MPG Max controller to the point at which even a novice is capable of getting the most from the system by inputting basic information.

During commuting, getting into boost and opening up the second nozzle, the power sprayer of the dual setup utilized by the Stage 3 MPG Max system granted us access to the passing lane for the first time. In trucker-speak, it feels as if the VW gained a gear upgrade. In enthusiast language, it was like finding out that behind the nerdy girl’s thick glasses was a hottie!

We have more in mods than we do in the car and it shows, but Project GTDI is consistently pumping out 55 mpg. A Stage 3 MPG Max, straightpipe and K&N drop-in into the project, and we’re laughing every time we drive past a Prius billboard.


Snow Performance


CGS Motorsports


The Diesel Shop


Looking Forward

Although there is an increased interest in the TDI market, only a few manufacturers are making parts for the TDI. ARP is one of the companies that have recently joined the market by providing head studs and main studs. When we ordered the studs for Project GTDI, the general reaction was, “You’re going to put head studs on that?” Yes, and for good reason, too.

Like a Power Stroke, Duramax and Cummins, the TDI generates a lot of cylinder pressure and is susceptible to head lifting if there’s too much boost. The principles of head studs carry over to the TDI, albeit on a much smaller scale. The larger stud and bolt belongs to a 6.0L Power Stroke, and the smaller is an ARP for our VW.

Just like the Snow water-meth, the VW diesel shows big gains in power without much effort. From here forward, expect to see similar performance mods that you’d see on other trucks in Diesel World … even down to compound turbos.

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